Scenario of the BUG#40731 ("Maria: hang (probably in page cache) under concurrency"):
      T1: Disable logging for the table
      T1: Start inserting into the table
      T2: Tries to lock the table so waits.
      T2: Tries unlock and relock during the process see that the table has disabled logging and reenables it
      T1: Got DBUG_ASSERT because suddenly start use table with transaction switched on which is not expected during bulk insert

storage/maria/ma_pagecache.c:
  Page type print added for debugging purposes.
storage/maria/ma_recovery.c:
  Check that it was this thred which switched off logging (transactional mode).
storage/maria/maria_def.h:
  Flag for controling which thread switched off transactiona mode for the table added.

Merge of 5.1-main into 5.1-maria. There were no changes to storage/myisam, or mysql-test/t/*myisam*.
However there were three new tests mysql-test/suite/parts/t/partition*myisam.test, of which I make here
copies for Maria.

storage/maria/trnman.c:
  During Maria's checkpoint, we walk the list of active transactions; in this list we may find a transaction with a short_id of 0 which means "uninitialized" (is being created right now) and want to ignore this transaction. Such short_id is set under trn->state_lock, so use this mutex to reliably read short_id during checkpoint.

storage/maria/ma_pagecache.c:
  Added correct reaction on find operation status during writing the page.

storage/maria/ma_pagecache.c:
  Added correct reaction on find operation status during writing the page.

            
Innodb monitor could cause a server crash because of invalid access to a
shared variable in a concurrent environment.
                  
This patch adds a guard to protect against crashes but not against
inconsistent values because of performance reasons.

sql/sql_class.cc:
  * Attempt snapshot of static memory pointer proc_info to avoid null pointers.

where it was forgotten to remove them.

refining the regression test to avoid explicit innodb engine in create.

Prevent this by modifying CFLAGS and CXXFLAGS.

Upmerge from 5.0, modified according to the different spec file structure.

support-files/mysql.spec.sh:
  Bug #40546  Debug server in RPM is built with compiler optimization
  
  Modify CFLAGS and CXXFLAGS for the duration of the debug server build
  (implemented by doing it in a subshell)
  so that they do not contain any optimization flag.
  Play it safe and prepare for both gcc and icc.

Prevent this by modifying CFLAGS and CXXFLAGS.

support-files/mysql.spec.sh:
  Bug #40546  Debug server in RPM is built with compiler optimization
  
  Modify CFLAGS and CXXFLAGS for the duration of the debug server build
  (implemented by doing it in a subshell)
  so that they do not contain any optimization flag.
  Play it safe and prepare for both gcc and icc.

Problem 1: BUG#36625: rpl_redirect doesn't do anything useful. It tests an
obsolete feature that was never fully implemented.
Fix 1: Remove rpl_redirect.
Problem 2: rpl_innodb_bug28430 and rpl_flushlog_loop are disabled despite the
bugs for which they were disabled have been fixed.
Fix 2: Re-enable rpl_innodb_bug28430 and rpl_flushlog_loop.


mysql-test/suite/rpl/r/rpl_redirect.result:
  Removed result file for obsolete test.\
mysql-test/suite/rpl/t/disabled.def:
  Re-enabled tests.
mysql-test/suite/rpl/t/rpl_redirect.test:
  Removed obsolete test.

storage/maria/trnman.c:
  Store min used trid in a global variable and change trnman_get_min_trid() to return this variable without using a mutex.
  This is safe as trnman_get_min_trid() is used for trid optimization and all algoritms will work even if it returns a slightly older trid.
  
  Also ensure that LOCK_trn_list is unlocked in trnman_new_trn() in the very unlikely case that lf_hash_get_pins() fails

The convert_constant_item function converts a constant to integer using
field for condition like 'field = a_constant'. In some cases the
convert_constant_item is called for a subquery when outer select is already
being executed, so convert_constant_item saves field's value to prevent its
corruption. For EXPLAIN and at the prepare phase field's value isn't
initialized yet, thus when convert_constant_item tries to restore saved
value it fails assertion.

Now the convert_constant_item doesn't save/restore field's value if it's
haven't been read yet. Outer constant values are always saved.

mysql-test/r/explain.result:
  Added a test case for the bug#37870.
mysql-test/t/explain.test:
  Added a test case for the bug#37870.
sql/item_cmpfunc.cc:
  Bug#37870: Usage of uninitialized value caused failed assertion.
  Now the convert_constant_item doesn't save/restore field's value if it's
  haven't been read yet. Outer constant values are always saved.

order by

Problem was that the first index read was unordered,
and the next was ordered, resulting in use of
uninitialized data.

Solution was to use the correct variable to see if
the 'next' call should be ordered or not.

mysql-test/r/partition.result:
  Bug#40494: MYSQL server crashes on range access with
  partitioning and order by
  
  Added test case for the bug.
mysql-test/t/partition.test:
  Bug#40494: MYSQL server crashes on range access with
  partitioning and order by
  
  Added test case for the bug.
sql/ha_partition.cc:
  Bug#40494: MYSQL server crashes on range access with
  partitioning and order by
  
  Used the wrong variable to decide to continue with
  ordered or unordered scan.